Metal vanadium oxide particles

ABSTRACT

Metal vanadium oxide particles have been produced with an average diameter less than about 500 nm. The particles are produced from nanocrystalline vanadium oxide particles. Silver vanadium oxide particles, for example, can be formed by the heat treatment of a mixture of nanoscale vanadium oxide and a silver compound. Other metal vanadium oxide particles can be produced by similar processes. The metal vanadium oxide particles have very uniform properties.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of commonly assigned U.S. patentapplication Ser. No. 09/246,076, filed Feb. 5, 1999, now U.S. Pat. No.6,225,007 to Horne et al., entitled “Metal Vanadium Oxide Particles,”incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to particles of metal vanadium oxide compositions.In particular, the invention relates to nanoscale metal vanadium oxideparticles, such as silver vanadium oxide particles, and correspondingmethods for producing nanoscale metal vanadium oxide particles.

BACKGROUND OF THE INVENTION

Lithium based batteries have become commercially successful due to theirrelatively high energy density. Suitable positive electrode materialsfor lithium based batteries include materials that can intercalatelithium atoms into their lattice. The negative electrode can be lithiummetal, lithium alloys or compounds that can reversibly intercalatelithium atoms into their lattice. Batteries formed from lithium metal orlithium alloy negative electrodes are referred to as lithium batterieswhile batteries formed with an anode (negative electrode) activematerial that can intercalate lithium ions are referred to as lithiumion batteries.

In order to produce improved batteries, various materials have beenexamined for use as cathode (positive electrode) active materials forlithium based batteries. A variety of materials, generallychalgogenides, are useful in lithium based batteries. For example,vanadium oxides in certain oxidation states are effective materials forthe production of positive electrodes for lithium based batteries. Also,metal vanadium oxide compositions have been identified as having highenergy densities and high power densities, when used in positiveelectrodes for lithium based batteries. Silver vanadium oxide has aparticularly high energy density and high power densities, when used inlithium based batteries. Silver vanadium oxide batteries have foundparticular use in the production of implantable cardiac defribulatorswhere the battery must be able to recharge a capacitor to deliver largepulses of energy in rapid succession, within ten seconds or less.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to a collection of particlescomprising metal vanadium oxide, the particles having an averagediameter less than about 500 nm.

In another aspect, the invention pertains to a method of producingparticles of metal vanadium oxide comprising heating a mixture ofvanadium oxide particles with a non-vanadium metal compound, thevanadium oxide particles having an average diameter less than about 500nm.

In a further aspect, the invention pertains to a battery comprising apositive electrode having active particles comprising metal vanadiumoxide within a binder, the active particles having an average diameterless than about 500 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, sectional view of an embodiment of a laserpyrolysis apparatus, where the cross section is taken through the middleof the laser radiation path. The upper insert is a bottom view of thecollection nozzle, and the lower insert is a top view of the deliverynozzle.

FIG. 2 is a schematic view of a reactant delivery apparatus for thedelivery of vapor reactants to the laser pyrolysis apparatus of FIG. 1.

FIG. 3 is schematic, side view of a reactant delivery apparatus for thedelivery of an aerosol reactant to the laser pyrolysis apparatus of FIG.1.

FIG. 4 is a schematic, perspective view of an elongated reaction chamberfor the performance of laser pyrolysis, where components of the reactionchamber are shown as transparent to reveal internal structure.

FIG. 5 is a sectional view of the reaction chamber of FIG. 4 taken alongline 5-5.

FIG. 6 is a schematic, sectional view of an apparatus for heat treatingnanoparticles, in which the section is taken through the center of theapparatus.

FIG. 7 is a schematic, sectional view of an oven for reactingnanoparticles under heat, in which the section is taken through themiddle of the oven.

FIG. 8 is a schematic, perspective view of an embodiment of a battery ofthe invention.

FIG. 9 is an x-ray diffractogram of crystalline VO₂ nanoparticles.

FIG. 10 is an x-ray diffractogram of crystalline V₂O₅ nanoparticlesproduced by heat treating nanoparticles of crystalline VO₂.

FIG. 11 is a transmission electron microscope view of crystalline V₂O₅nanoparticles.

FIG. 12 is a plot depicting the distribution of particle sizes for thecrystalline V₂O₅ nanoparticles depicted in FIG. 11.

FIG. 13 is a plot of four x-ray diffractograms of silver vanadium oxideproduced by heat treating nanocrystalline V₂O₅ with silver nitrate in anoxygen atmosphere, where each diffractogram was produced with materialsformed under different conditions.

FIG. 14 is a plot of three x-ray diffractograms of silver vanadium oxideproduced by heat treating nanocrystalline V₂O₅ with silver nitrate in anargon atmosphere, where each diffractogram was produced with materialsformed under different conditions.

FIG. 15 is a transmission electron microscope view of silver vanadiumoxide nanoparticles.

FIG. 16 is a transmission electron microscope view of the V₂O₅nanoparticle samples used to produce the silver vanadium oxide particlesshown in FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Vanadium oxide nanoparticles can be used to form metal vanadium oxidenanoparticles, such as silver vanadium oxide nanoparticles. Vanadiumoxide nanoparticles with various stoichiometries and crystal structurescan be produced by laser pyrolysis alone or with additional processing.These various forms of vanadium oxide nanoparticles can be used asstarting materials for the formation of metal vanadium oxidenanoparticles. The nanoparticles are formed by mixing the vanadium oxidenanoparticles with a compound of the metal to be introduced into thevanadium oxide to form a material with both metals in the lattice. Byusing appropriately selected processing conditions, the particlesincorporating both metals can be formed without losing the nanoscalecharacter of the initial vanadium oxide nanoparticles.

Preferred collections of metal vanadium oxide particles have an averagediameter less than a micron and a very narrow distribution of particlediameters. In particular, the distribution of particle diameterspreferably does not have a tail. In other words, there are effectivelyno particles with a diameter an order of magnitude greater than theaverage diameter such that the particle size distribution rapidly dropsto zero.

To generate vanadium oxide nanoparticle starting materials for furtherprocessing into metal vanadium oxides, laser pyrolysis is used eitheralone or in combination with additional processing. Specifically, laserpyrolysis has been found to be an excellent process for efficientlyproducing vanadium oxide nanoparticles with a narrow distribution ofaverage particle diameters. In addition, nanoscale vanadium oxideparticles produced by laser pyrolysis can be subjected to heating undermild conditions in an oxygen environment or an inert environment toalter the crystal properties of the vanadium oxide particles withoutdestroying the nanoparticle size. The stoichiometry and crystalstructure of the vanadium oxide nanoparticles produced by laserpyrolysis can be modified by heat processing in an oven. Thus, a varietyof different types of vanadium oxide based nanoparticles can beproduced.

A basic feature of successful application of laser pyrolysis for theproduction of vanadium oxide nanoparticles is production of a reactantstream containing a vanadium precursor, a radiation absorber and anoxygen source. The reactant stream is pyrolyzed by an intense lightbeam, such as a laser beam. The laser pyrolysis provides for formationof phases of materials that are difficult to form under thermodynamicequilibrium conditions. As the reactant stream leaves the light beam,the vanadium oxide particles are rapidly quenched.

The metal vanadium oxide particles are formed by a thermal process. Asecond metal precursor comprises a non-vanadium transition metal.Preferred second metal precursors include compositions with copper,silver or gold. The second metal precursor compound is mixed with acollection of vanadium oxide nanoparticles and heated to form theparticles incorporating both metals. Under suitably mild conditions, theheat processing is effective to produce the particles while notdestroying the nanoscale of the initial vanadium oxide particles.

As noted above, lithium atoms and/or ions can intercalate into variousforms of vanadium oxide and metal vanadium oxide particles. To form apositive electrode, which acts as a cathode upon discharge of the cell,the metal vanadium oxide nanoparticles can be incorporated into a filmwith a binder such as a polymer. The film preferably incorporatesadditional electrically conductive particles held by a binder along withthe metal vanadium oxide particles. The film can be used as a positiveelectrode in a lithium battery or a lithium ion battery.

A. Vanadium Oxide Nanoparticle Production

Laser pyrolysis has been discovered to be a valuable tool for theproduction of nanoscale vanadium oxide particles. In addition, theparticles produced by laser pyrolysis are a convenient material forfurther processing to expand the pathways for the production ofdesirable vanadium oxide particles. Thus, using laser pyrolysis alone orin combination with additional processes, a wide variety of vanadiumoxide particles can be produced.

The reaction conditions determine the qualities of the particlesproduced by laser pyrolysis. The reaction conditions for laser pyrolysiscan be controlled relatively precisely in order to produce particleswith desired properties. The appropriate reaction conditions to producea certain type of particles generally depend on the design of theparticular apparatus. Specific conditions used to produce vanadium oxideparticles in a particular apparatus are described below in the Examples.Additional information on the production of vanadium oxide nanoparticlesby laser pyrolysis is provided in copending and commonly assigned U.S.patent application Ser. No. 08/897,778 to Bi et al. now U.S. Pat. No.6,106,798, entitled “Vanadium Oxide Nanoparticles,” incorporated hereinby reference. Furthermore, some general observations on the relationshipbetween reaction conditions and the resulting particles can be made.

Increasing the laser power results in increased reaction temperatures inthe reaction region as well as a faster quenching rate. A rapidquenching rate tends to favor production of high energy phases, whichmay not be obtained with processes near thermal equilibrium. Similarly,increasing the chamber pressure also tends to favor the production ofhigher energy structures. Also, increasing the concentration of thereactant serving as the oxygen source in the reactant stream favors theproduction of particles with increased amounts of oxygen.

Reactant flow rate and velocity of the reactant gas stream are inverselyrelated to particle size so that increasing the reactant gas flow rateor velocity tends to result in smaller particle size. Also, the growthdynamics of the particles have a significant influence on the size ofthe resulting particles. In other words, different forms of a productcompound have a tendency to form different size particles from otherphases under relatively similar conditions. Laser power also influencesparticle size with increased laser power favoring larger particleformation for lower melting materials and smaller particle formation forhigher melting materials.

Laser pyrolysis has been performed generally with gas phase reactants.The use of exclusively gas phase reactants is somewhat limiting withrespect to the types of precursor compounds that can be used. Thus,techniques have been developed to introduce aerosols containing reactantprecursors into laser pyrolysis chambers. The aerosol atomizers can bebroadly classified as ultrasonic atomizers, which use an ultrasonictransducer to form the aerosol, or as mechanical atomizers, which useenergy from one or more flowing fluids (liquids, gases, or supercriticalfluids) themselves to form the aerosol. Improved aerosol deliveryapparatuses for reactant systems are described further in copending andcommonly assigned U.S. patent application Ser. No. 09/188,670, now U.S.Pat. No. 6,193,936, filed on Nov. 9, 1998, entitled “Reactant DeliveryApparatuses,” incorporated herein by reference.

Using aerosol delivery apparatuses, solid precursor compounds can bedelivered by dissolving the compounds in a solvent. Alternatively,powdered precursor compounds can be dispersed in a liquid\solvent foraerosol delivery. Liquid precursor compounds can be delivered as anaerosol from a neat liquid, a liquid/gas mixture, liquid mixtures or aliquid solution, if desired. Aerosol reactants can be used to obtainsignificant reactant throughput. The solvent, if any, can be selected toachieve desired properties of the solution. Suitable solvents includewater, methanol, ethanol and other organic solvents. The solvent shouldhave a desired level of purity such that the resulting particles have adesired purity level.

If the aerosol precursors are formed with a solvent present, the solventis rapidly evaporated by the laser beam in the reaction chamber suchthat a gas phase reaction can take place. Thus, the fundamental featuresof the laser pyrolysis reaction are unchanged. However, the reactionconditions are affected by the presence of the aerosol. Suitableconditions for the formation of manganese oxide nanoparticles by laserpyrolysis with aerosol precursors is described in copending and commonlyassigned U.S. patent application Ser. No. 09/188,770, filed on Nov. 9,1998, now U.S. Pat. No. 6,506,493, entitled “Metal Oxide Particles,”incorporated herein by reference. Suitable vanadium precursors foraerosol production include, for example, vanadium trichloride (VCl₃),vanadyl chloride (VOCl), and vanadyl dichloride (VOCl₂), which issoluble in absolute alcohol.

The compounds are dissolved in a solution preferably with aconcentration greater than about 0.5 molar. Generally, the greater theconcentration of precursor in the solution the greater the throughput ofreactant through the reaction chamber. As the concentration increases,however, the solution can become more viscous such that the aerosol hasdroplets with larger sizes than desired. Thus, selection of solutionconcentration can involve a balance of factors in the selection of apreferred solution concentration.

Appropriate vanadium precursor compounds for vapor delivery generallyinclude vanadium compounds with reasonable vapor pressures, i.e., vaporpressures sufficient to get desired amounts of precursor vapor in thereactant stream. The vessel holding the precursor compounds can beheated to increase the vapor pressure of the vanadium precursor, ifdesired. Suitable vanadium precursors include, for example, VCl₄, VCCl,V(CO)₆ and VOCl₃. The chlorine in these representative precursorcompounds can be replaced with other halogens, e.g., Br, I and F.

Preferred secondary reactants serving as oxygen source include, forexample, O₂, CO, CO₂, O₃ and mixtures thereof. The secondary reactantcompound should not react significantly with the vanadium precursorprior to entering the reaction zone since this generally would result inthe formation of large particles.

Laser pyrolysis can be performed with a variety of optical lightfrequencies. Preferred light sources include lasers, especially lasersthat operate in the infrared portion of the electromagnetic spectrum.CO₂ lasers are particularly preferred sources of light. Infraredabsorbers for inclusion in the molecular stream include, for example,C₂H₄, NH₃, SF₆, SiH₄ and O₃. O₃ can act as both an infrared absorber andas an oxygen source. Alternatively, a solvent, such as isopropylalcohol, in a liquid delivered by aerosol can absorb light from thelight beam. The radiation absorber, such as the infrared absorber,absorbs energy from the radiation beam and distributes the energy to theother reactants to drive the pyrolysis.

Preferably, the energy absorbed from the radiation beam increases thetemperature at a tremendous rate, many times the rate that energygenerally would be produced even by strongly exothermic reactions undercontrolled condition. While the process generally involvesnonequilibrium conditions, the temperature can be describedapproximately based on the heat in the absorbing region. The laserpyrolysis process is qualitatively different from the process in acombustion reactor where an energy source initiates a reaction, but thereaction is driven by energy given off by an exothermic reaction.

An inert shielding gas can be used to reduce the amount of reactant andproduct molecules contacting the reactant chamber components.Appropriate shielding gases include, for example, Ar, He and N₂. Inertgas can also be mixed with the reactant stream to moderate the reaction.

An appropriate laser pyrolysis apparatus generally includes a reactionchamber isolated from the ambient environment. A reactant inletconnected to a reactant supply system produces a reactant stream throughthe reaction chamber. A light beam path intersects the reactant streamat a reaction zone. The reactant stream continues after the reactionzone to an outlet, where the reactant stream exits the reaction chamberand passes into a collection system. Generally, the light source islocated external to the reaction chamber, and the light beam enters thereaction chamber through an appropriate window.

Referring to FIG. 1, a particular embodiment 100 of a laser pyrolysisapparatus involves a reactant supply system 102, reaction chamber 104,collection system 106, light source 108 and shielding gas deliverysystem 110. Two alternative reaction supply systems can be used with theapparatus of FIG. 1. The first reaction supply system is used to deliverexclusively gaseous reactants. The second reactant supply system is usedto deliver one or more reactants as an aerosol. Variations on thesereaction supply systems can also be used.

Referring to FIG. 2, a first embodiment 112 of reactant supply system102 includes a source 120 of precursor compound. For liquid or solidprecursors, a carrier gas from carrier gas source 122 can be introducedinto precursor source 120 to facilitate delivery of the precursor as avapor. The carrier gas from source 122 preferably is either an infraredabsorber or an inert gas and is preferably bubbled through a liquidprecursor compound or delivered into a solid precursor delivery system.Inert gas used as a carrier gas can moderate the reaction conditions.The quantity of precursor vapor in the reaction zone is roughlyproportional to the flow rate of the carrier gas.

Alternatively, carrier gas can be supplied directly from infraredabsorber source 124 or inert gas source 126, as appropriate. Thesecondary reactant is supplied from reactant source 128, which can be agas cylinder or other suitable container. The gases from the precursorsource 120 are mixed with gases from reactant source 128, infraredabsorber source 124 and inert gas source 126 by combining the gases in asingle portion of tubing 130. The gases are combined a sufficientdistance from reaction chamber 104 such that the gases become well mixedprior to their entrance into reaction chamber 104.

The combined gas in tube 130 passes through a duct 132 into rectangularchannel 134, which forms part of an injection nozzle for directingreactants into the reaction chamber. Portions of reactant supply system112 can be heated to inhibit the deposition of precursor compound on thewalls of the delivery system.

Flow from sources 122, 124, 126 and 128 are preferably independentlycontrolled by mass flow controllers 136. Mass flow controllers 136preferably provide a controlled flow rate from each respective source.Suitable mass flow controllers include, for example, Edwards Mass FlowController, Model 825 series, from Edwards High Vacuum International,Wilmington, Mass.

Referring to FIG. 3, an alternative embodiment 150 of the reactantsupply system 102 is used to supply an aerosol to channel 134. Channel134 forms part of an injection nozzle for directing reactants into thereaction chamber and terminates at the reactant inlet. Reactant supplysystem 150 includes an aerosol generator 152, carrier gas supply tube154 and junction 156. Channel 134, aerosol generator 152 and carrier gassupply tube 154 meet within interior 158 within junction 156. Carriergas supply tube 154 is oriented to direct carrier gas along channel 134.

Aerosol generator 152 is mounted such that an aerosol 160 is generatedin the volume of chamber 158 between the opening into channel 134 andthe outlet from supply tube 154. In a preferred embodiment, aerosolgenerator 152 generates an aerosol with momentum roughly orthogonal tothe carrier gas flow from tube 154 to channel 134. Thus, carrier gasfrom supply tube 154 directs aerosol precursor generated by aerosolgenerator 152 into channel 134.

Aerosol generator 152 can operate based on a variety of principles. Forexample, the aerosol can be produced with an ultrasonic nozzle, with anelectrostatic spray system, with a pressure-flow or simplex atomizer,with an effervescent atomizer or with a gas atomizer where liquid isforced under significant pressure through a small orifice and fracturedinto particles by a colliding gas stream. Suitable ultrasonic nozzlescan include piezoelectric transducers. Ultrasonic nozzles withpiezoelectric transducers and suitable broadband ultrasonic generatorsare available from Sono-Tek Corporation, Milton, N.Y., such as model8700-120. Suitable aerosol generators are described further in copendingand commonly assigned, U.S. patent application Ser. No. 09/188,670, nowU.S. Pat. No. 6,193,936 to Gardner et al., entitled “REACTANT DELIVERYAPPARATUSES,” incorporated herein by reference. Additional aerosolgenerators can be attached to junction 156 through other ports 162 suchthat additional aerosols can be generated in interior 158 for deliveryinto the reaction chamber.

Junction 156 includes ports 162 to provide access from outside junction156 to interior 158. Thus, channel 134, aerosol generator 152 and tube154 can be mounted appropriately. In one embodiment, junction 156 iscubic with six cylindrical ports 162, with one port 162 extending fromeach face of junction 156. Junction 156 can be made from stainless steelor other durable, noncorrosive material. A window 161 preferably issealed at one port 162 to provide for visual observation into interior158. The port 162 extending from the bottom of junction 156 preferablyincludes a drain 163, such that condensed aerosol that is not deliveredthrough channel 134 can be removed from junction 156.

Carrier gas supply tube 154 is connected to gas source 164. Gas source164 can include a plurality of gas containers that are connected todeliver a selected gas or gas mixture to supply tube 154. Thus, carriergas supply tube 154 can be used to deliver a variety of gases desiredwithin the reactant stream including, for example, laser absorbinggases, reactants, and/or inert gases. The flow of gas from gas source164 to supply tube 154 is controlled by one or more mass flowcontrollers 166. Liquid supply tube 168 is connected to aerosolgenerator 152. Liquid supply tube 168 is connected to liquid supply 170.

In operation, carrier gas flow directs the aerosol delivered withinchamber 158 into channel 134. In this way, the delivery velocity of theaerosol is determined by the flow rate of the carrier gas. Inalternative embodiments, the aerosol generator is placed at an upwardangle relative to the horizontal, such that a component of the forwardmomentum of the aerosol is directed along channel 134. In a preferredembodiment, the output directed from the aerosol generator is placed atabout a 45° angle relative to the normal direction defined by theopening into channel 134, i.e. the direction of the flow into channel134 from supply tube 154.

Referring to FIG. 1, shielding gas delivery system 110 includes inertgas source 190 connected to an inert gas duct 192. Inert gas duct 192flows into annular channel 194. A mass flow controller 196 regulates theflow of inert gas into inert gas duct 192. If reactant delivery system112 is used, inert gas source 126 can also function as the inert gassource for duct 192, if desired.

The reaction chamber 104 includes a main chamber 200. Reactant supplysystem 102 connects to the main chamber 200 at injection nozzle 202.Reaction chamber 104 can be heated to keep the precursor compound in thevapor state. Similarly, the argon shielding gas preferably can beheated. The chamber can be examined for condensation to ensure thatprecursor is not deposited in the chamber.

The end of injection nozzle 202 has an annular opening 204 for thepassage of inert shielding gas, and a reactant inlet 206 for the passageof reactants to form a reactant stream in the reaction chamber. Reactantinlet 206 preferably is a slit, as shown in FIG. 1. Annular opening 204has, for example, a diameter of about 1.5 inches and a width along theradial direction from about ⅛ in to about 1/16 in. The flow of shieldinggas through annular opening 204 helps to prevent the spread of thereactant gases and product particles throughout reaction chamber 104.

Tubular sections 208, 210 are located on either side of injection nozzle202. Tubular sections 208, 210 include ZnSe windows 212, 214,respectively. Windows 212, 214 are about 1 inch in diameter. Windows212, 214 are preferably cylindrical lenses with a focal length equal tothe distance between the center of the chamber to the surface of thelens to focus the beam to a point just below the center of the nozzleopening. Windows 212, 214 preferably have an antireflective coating.Appropriate ZnSe lenses are available from Janos Technology, Townshend,Vt. Tubular sections 208, 210 provide for the displacement of windows212, 214 away from main chamber 200 such that windows 212, 214 are lesslikely to be contaminated by reactants and/or products. Window 212, 214are displaced, for example, about 3 cm from the edge of the main chamber200.

Windows 212, 214 are sealed with a rubber o-ring to tubular sections208, 210 to prevent the flow of ambient air into reaction chamber 104.Tubular inlets 216, 218 provide for the flow of shielding gas intotubular sections 208, 210 to reduce the contamination of windows 212,214. Tubular inlets 216, 218 are connected to inert gas source 138 or toa separate inert gas source. In either case, flow to inlets 216, 218preferably is controlled by a mass flow controller 220.

Light source 108 is aligned to generate a light beam 222 that enterswindow 212 and exits window 214. Windows 212, 214 define a light paththrough main chamber 200 intersecting the flow of reactants at reactionzone 224. After exiting window 214, light beam 222 strikes power meter226, which also acts as a beam dump. An appropriate power meter isavailable from Coherent Inc., Santa Clara, Calif. Light source 108preferably is a laser, although it can be an intense conventional lightsource such as an arc lamp. Preferably, light source 108 is an infraredlaser, especially a CW CO₂ laser such as an 1800 watt maximum poweroutput laser available from PRC Corp., Landing, N.J.

Reactants passing through reactant inlet 206 in injection nozzle 202initiate a reactant stream. The reactant stream passes through reactionzone 224, where reaction involving the vanadium precursor compound takesplace. Heating of the gases in reaction zone 224 generally is extremelyrapid, roughly on the order of 10⁵ degree C./sec depending on thespecific conditions. The reaction is rapidly quenched upon leavingreaction zone 224, and particles 228 are formed in the reactant stream.The nonequilibrium nature of the process allows for the production ofnanoparticles with a highly uniform size distribution and structuralhomogeneity.

The path of the reactant/product stream continues to collection nozzle230. Collection nozzle 230 is spaced about 2 cm from injection nozzle202. The small spacing between injection nozzle 202 and collectionnozzle 230 helps reduce the contamination of reaction chamber 104 withreactants and products. Collection nozzle 230 has a circular opening232. Circular opening 232 feeds into collection system 106.

The chamber pressure is monitored with a pressure gauge attached to themain chamber. The preferred chamber pressure for the production of thedesired oxides generally ranges from about 80 Torr to about 500 Torr.

Reaction chamber 104 has two additional tubular sections not shown. Oneof the additional tubular sections projects into the plane of thesectional view in FIG. 1, and the second additional tubular sectionprojects out of the plane of the sectional view in FIG. 1. When viewedfrom above, the four tubular sections are distributed roughly,symmetrically around the center of the chamber. These additional tubularsections have windows for observing the inside of the chamber. In thisconfiguration of the apparatus, the two additional tubular sections arenot used to facilitate production of particles.

Collection system 106 preferably includes a curved channel 270 leadingfrom collection nozzle 230. Because of the small size of the particles,the product particles follow the flow of the gas around curves.Collection system 106 includes a filter 272 within the gas flow tocollect the product particles. Due to curved section 270, the filter isnot supported directly above the chamber. A variety of materials such asTeflon, glass fibers and the like can be used for the filter as long asthe material is inert and has a fine enough mesh to trap the particles.Preferred materials for the filter include, for example, a glass fiberfilter from ACE Glass Inc., Vineland, N.J. and cylindrical Nomex® fiberfilters from AF Equipment Co., Sunnyvale, Calif.

Pump 274 is used to maintain collection system 106 at a selectedpressure. A variety of different pumps can be used. Appropriate pumpsfor use as pump 274 include, for example, Busch Model B0024 pump fromBusch, Inc., Virginia Beach, Va. with a pumping capacity of about 25cubic feet per minute (cfm) and Leybold Model SV300 pump from LeyboldVacuum Products, Export, Pa. with a pumping capacity of about 195 cfm.It may be desirable to flow the exhaust of the pump through a scrubber276 to remove any remaining reactive chemicals before venting into theatmosphere. The entire apparatus 100 can be placed in a fume hood forventilation purposes and for safety considerations. Generally, the laserremains outside of the fume hood because of its large size.

The apparatus is controlled by a computer. Generally, the computercontrols the laser and monitors the pressure in the reaction chamber.The computer can be used to control the flow of reactants and/or theshielding gas. The pumping rate is controlled by either a manual needlevalve or an automatic throttle valve inserted between pump 274 andfilter 272. As the chamber pressure increases due to the accumulation ofparticles on filter 272, the manual valve or the throttle valve can beadjusted to maintain the pumping rate and the corresponding chamberpressure.

The reaction can be continued until sufficient particles are collectedon filter 272 such that the pump can no longer maintain the desiredpressure in the reaction chamber 104 against the resistance throughfilter 272. When the pressure in reaction chamber 104 can no longer bemaintained at the desired value, the reaction is stopped, and filter 272is removed. With this embodiment, about 1-300 grams of particles can becollected in a single run before the chamber pressure can no longer bemaintained. A single run generally can last up to about 10 hoursdepending on the type of particle being produced and the type of filterbeing used.

The reaction conditions can be controlled relatively precisely. The massflow controllers are quite accurate. The laser generally has about 0.5percent power stability. With either a manual control or a throttlevalve, the chamber pressure can be controlled to within about 1 percent.

The configuration of the reactant supply system 102 and the collectionsystem 106 can be reversed. In this alternative configuration, thereactants are supplied from the top of the reaction chamber, and theproduct particles are collected from the bottom of the chamber. In thisconfiguration, the collection system may not include a curved section sothat the collection filter is mounted directly below the reactionchamber.

An alternative design of a laser pyrolysis apparatus has been describedin copending and commonly assigned U.S. patent application Ser. No.08/808,850 now U.S. Pat. No. 5,958,348, entitled “Efficient Productionof Particles by Chemical Reaction,” incorporated herein by reference.This alternative design is intended to facilitate production ofcommercial quantities of particles by laser pyrolysis. The reactionchamber is elongated along the laser beam in a dimension perpendicularto the reactant stream to provide for an increase in the throughput ofreactants and products. The original design of the apparatus was basedon the introduction of purely gaseous reactants. Alternative embodimentsfor the introduction of an aerosol into an elongated reaction chamber isdescribed in copending and commonly assigned U.S. patent applicationSer. No. 09/188,670 to Gardner et al., filed on Nov. 9, 1998, now U.S.Pat. No. 6,193,936, entitled “Reactant Delivery Apparatuses,”incorporated herein by reference.

In general, the alternative pyrolysis apparatus includes a reactionchamber designed to reduce contamination of the chamber walls, toincrease the production capacity and to make efficient use of resources.To accomplish these objectives, an elongated reaction chamber is usedthat provides for an increased throughput of reactants and productswithout a corresponding increase in the dead volume of the chamber. Thedead volume of the chamber can become contaminated with unreactedcompounds and/or reaction products.

The design of the improved reaction chamber 300 is shown schematicallyin FIGS. 4 and 5. A reactant inlet 302 enters the main chamber 304.Reactant inlet 302 provides for the introduction of gaseous and/oraerosol reactants into main chamber 304. Reactant inlet 302 conformsgenerally to the shape of main chamber 304. Main chamber 304 includes anoutlet 306 along the reactant/product stream for removal of particulateproducts, any unreacted gases and inert gases. Shielding gas inlets 310are located on both sides of reactant inlet 302. Shielding gas inletsare used to form a blanket of inert gases on the sides of the reactantstream to inhibit contact between the chamber walls and the reactantsand products.

Tubular sections 320, 322 extend from the main chamber 304. Tubularsections 320, 322 hold windows 324, 326 to define a laser beam path 328through the reaction chamber 300. Tubular sections 320, 322 can includeinert gas inlets 330, 332 for the introduction of inert gas into tubularsections 320, 322.

The dimensions of elongated reactant inlet 316 preferably are designedfor high efficiency particle production. Reasonable dimensions for thereactant inlet for the production of vanadium oxide nanoparticle, whenused with a 1800 watt CO₂ laser, are from about 5 mm to about 1 meter.

The improved apparatus includes a collection system to remove thenanoparticles from the molecular stream. The collection system can bedesigned to collect a large quantity of particles without terminatingproduction or, preferably, to run in continuous production by switchingbetween different particle collectors within the collection system. Thecollection system can include curved components within the flow pathsimilar to curved portion of the collection system shown in FIG. 1. Aparticular preferred collection system for particle production systemsoperating in a continuous collection mode is described in copending andcommonly assigned U.S. patent application Ser. No. 09/107,729, now U.S.Pat. No. 6,270,732 to Gardner et al., entitled “Particle CollectionApparatus And Associated Methods,” incorporated herein by reference. Abatch collection system for use with the improved reaction system isdescribed in copending and commonly assigned U.S. patent applicationSer. No. 09/188,770, filed on Nov. 9, 1998, now U.S. Pat. No. 6,506,493,entitled “Metal Oxide Particles,” incorporated herein by reference. Theconfiguration of the reactant injection components and the collectionsystem can be reversed such that the particles are collected at the topof the apparatus.

As noted above, properties of the vanadium oxide particles can bemodified by further processing. The starting material for the heattreatment can be any type of solid vanadium oxide compound. Suitablematerials include, for example, VO, VO_(1.27), VO₂, V₂O₃, V₃O₅ andamorphous V₂O₅. The starting materials generally can be particles of anysize and shape. In addition, particles used as starting material canhave been subjected to one or more prior heating steps under differentconditions.

Nanoscale particles are preferred starting materials. The nanoscaleparticles have an average diameter of less than about 1000 nm andpreferably from about 5 nm to about 500 nm, and more preferably fromabout 5 nm to about 150 nm. Suitable nanoscale starting materials havebeen produced by laser pyrolysis.

The vanadium oxide particles are preferably heated in an oven or thelike to provide generally uniform heating. The processing conditionsgenerally are mild, such that significant amounts of particle sinteringdoes not occur. The temperature of heating preferably is low relative tothe melting point of both the starting material and the productmaterial. For nanoparticles, the processing temperature generally rangesfrom about 50° C. to about 500° C., and more preferably from about 60°C. to about 400° C.

The heating preferably is continued for greater than about 5 minutes,and generally is continued for from about 2 hours to about 100 hours,preferably from about 2 hours to about 50 hours. For certain targetproduct particles, additional heating does not lead to further variationin the particle composition. The atmosphere for the heating process canbe an oxidizing atmosphere or an inert atmosphere. In particular, forconversion of amorphous particles to crystalline particles or from onecrystalline structure to a different crystalline structure ofessentially the same stoichiometry, the atmosphere generally can beinert. The atmosphere over the particles can be static, or gases can beflowed through the system.

Appropriate oxidizing gases include, for example, O₂, O₃, CO, CO₂, andcombinations thereof. The O₂ can be supplied as air. Oxidizing gasesoptionally can be mixed with inert gases such as Ar, He and N₂. Wheninert gas is mixed with the oxidizing gas, the gas mixture can be fromabout 1 percent oxidizing gas to about 99 percent oxidizing gas, andmore preferably from about 5 percent oxidizing gas to about 99 percentoxidizing gas. Alternatively, either essentially pure oxidizing gas orpure inert gas can be used, as desired.

The precise conditions can be altered to vary the type of vanadium oxideproduct produced. For example, the temperature, time of heating, heatingand cooling rates, the gases and the exposure conditions with respect tothe gases can all be changed, as desired. Generally, while heating underan oxidizing atmosphere, the longer the heating period the more oxygenthat is incorporated into the material, prior to reaching equilibrium.Once equilibrium conditions are reached, the overall conditionsdetermine the crystalline phase of the powders.

A variety of ovens or the like can be used to perform the heating. Anexample of an apparatus 400 to perform this processing is displayed inFIG. 6. Apparatus 400 includes a jar 402, which can be made from glassor other inert material, into which the particles are placed. Suitableglass reactor jars are available from Ace Glass (Vineland, N.J.). Thetop of glass jar 402 is sealed to a glass cap 404, with a Teflon® gasket405 between jar 402 and cap 404. Cap 404 can be held in place with oneor more clamps. Cap 404 includes a plurality of ports 406, each with aTeflon® bushing. A multiblade stainless steel stirrer 408 preferably isinserted through a central port 406 in cap 404. Stirrer 408 is connectedto a suitable motor.

One or more tubes 410 are inserted through ports 406 for the delivery ofgases into jar 402. Tubes 410 can be made from stainless steel or otherinert material. Diffusers 412 can be included at the tips of tubes 410to disburse the gas within jar 402. A heater/furnace 414 generally isplaced around jar 402. Suitable resistance heaters are available fromGlas-col (Terre Haute, Ind.). One port preferably includes aT-connection 416. The temperature within jar 402 can be measured with athermocouple 416 inserted through T-connection 416. T-connection 416 canbe further connected to a vent 418. Vent 418 provides for the venting ofgas circulated through jar 402. Preferably vent 418 is vented to a fumehood or alternative ventalation equipment.

Preferably, desired gases are flowed through jar 402. Tubes 410generally are connected to an oxidizing gas source and/or an inert gassource. Oxidizing gas, inert gas or a combination thereof to produce thedesired atmosphere are placed within jar 402 from the appropriate gassource(s). Various flow rates can be used. The flow rate preferably isbetween about 1 standard cubic centimeters per minute (sccm) to about1000 sccm and more preferably from about 10 sccm to about 500 sccm. Theflow rate generally is constant through the processing step, althoughthe flow rate and the composition of the gas can be variedsystematically over time during processing, if desired. Alternatively, astatic gas atmosphere can be used.

VO₂, a material with a high melting point, is relatively easy to form inthe laser pyrolysis apparatuses described above. VO₂ is a suitablestarting product for oxidation to other forms of vanadium oxide. Someempirical adjustment may be required to produce the conditionsappropriate to generate a desired material. In addition, the heatprocessing can result in an alteration of the crystal lattice and/orremoval of adsorbed compounds on the particles to improve the quality ofthe particles.

For the processing of vanadium oxide, for example, the temperaturespreferably range from about 50° C. to about 500° C. and more preferablyfrom about 60° C. to about 400° C. The particles preferably are heatedfor about 5 minutes to about 100 hours. Some empirical adjustment may berequired to produce the conditions appropriate for yielding a desiredmaterial. The use of mild conditions avoids interparticle sinteringresulting in larger particle sizes. Some controlled sintering of theparticles can be performed at somewhat higher temperatures to produceslightly larger, average particle diameters.

The conditions to convert crystalline VO₂ to orthorhombic V₂O₅ and 2-Dcrystalline V₂O₅, and amorphous V₂O₅ to orthorhombic V₂O₅ and 2-Dcrystalline V₂O₅ are describe in copending and commonly assigned U.S.patent application Ser. No. 08/897,903, to Bi et al. now U.S. Pat. No.5,989,514, entitled “Processing of Vanadium Oxide Particles With Heat,”incorporated herein by reference.

B. Formation of Metal Vanadium Oxide Particles

It has been discovered that heat processing can be used to formnanoscale metal vanadium oxide particles. In a preferred approach to thethermal formation of metal vanadium oxide particles, vanadium oxidenanoscale particles first are mixed with a non-vanadium metal compound.The resulting mixture is heated in an oven to form a metal vanadiumoxide composition. The heat processing to incorporate metal into thevanadium oxide lattice can be performed in an oxidizing environment oran inert environment. In either type of environment, the heating stepgenerally results in alteration of the oxygen to vanadium ratio. Inaddition, the heat processing can result in an alteration of the crystallattice and/or removal of adsorbed compounds on the particles to improvethe quality of the particles.

The use of sufficiently mild conditions, i.e., temperatures well belowthe melting point of the vanadium oxide particles, results in metalincorporation into the vanadium oxide particles without significantlysintering the particles into larger particles. The vanadium oxideparticles used for the process preferably are nanoscale vanadium oxideparticles. It has been discovered that metal vanadium oxide compositionscan be formed from vanadium oxides with an oxidation state of +5 or lessthan +5. In particular, vanadium oxides with an oxidation states from +2(VO) to +5 (V₂O₅) can be used to form metal vanadium oxide particles.

Generally, the metal incorporated into the metal vanadium oxide particleis any non-vanadium transition metal. Preferred metals for incorporationinto the vanadium oxide include, for example, copper, silver, gold, andcombinations thereof. Suitable silver compounds include, for example,silver nitrate (AgNO₃). Suitable copper compounds include, for example,cupric nitrate (Cu(NO₃)₂). Alternatively, silver metal powder, coppermetal powder or gold metal powder can be used as sources of therespective metals.

Appropriate oxidizing gases include, for example, O₂ (supplied as air,if desired), O₃, CO, CO₂ and combinations thereof. The reactant gas canbe diluted with inert gases such as Ar, He and N₂. Alternatively, thegas atmosphere can be exclusively inert gas. Silver vanadium oxideparticles have been produced with either an inert atmosphere or anoxidizing atmosphere, as described in the Examples below.

A variety of apparatuses can be used to perform the heat processing forlithiation and/or annealing of a sample. An embodiment of a suitableapparatus 400 is described above with respect to FIG. 6 for the heatprocessing of vanadium oxides produced by laser pyrolysis. Analternative apparatus 430 for the incorporation of a metal into thevanadium oxide lattice is shown in FIG. 7. The particles are placedwithin a small vial 432, boat or the like within tube 434. Preferably,the desired gases are flowed through tube 434. Gases can be supplied forexample from inert gas source 436 or oxidizing gas source 438.

Tube 434 is located within oven or furnace 440. Oven 440 can be adaptedfrom a commercial furnace, such as Mini-Mite™ 1100° C. Tube Furnace fromRevco/Lindberg, Asheville, N.C. Oven 436 maintains the relevant portionsof the tube at a relatively constant temperature, although thetemperature can be varied systematically through the processing step, ifdesired. The temperature can be monitored with a thermocouple 442.

To form metal vanadium oxide particles in the heating step, a mixture ofvanadium oxide particles and the metal compound can be placed in tube434 within a vial 432. Preferably, a solution of the metal compound ismixed with the vanadium oxide nanoparticles and evaporated to drynessprior to further heating in the oven. The evaporation can be performedsimultaneously with the heating to form the metal vanadium oxidecomposition, if desired. For example, silver nitrate and copper nitratecan be applied to the vanadium oxide particles as an aqueous solution.Alternatively, vanadium oxide nanoparticles can be mixed with a drypowder of the metal compound or elemental metal powder, thereby avoidingthe evaporation step. A sufficient amount of the metal compound orelemental metal powder is added to yield the desired amount ofincorporation of the metal into the vanadium oxide lattice. Thisincorporation into the vanadium oxide lattice can be checked, forexample, through the use of x-ray diffractometry, as described below.

The precise conditions including type of oxidizing gas (if any),concentration of oxidizing gas, pressure or flow rate of gas,temperature and processing time can be selected to produce the desiredtype of product material. The temperatures generally are mild, i.e.,significantly below the melting point of the materials. The use of mildconditions avoids interparticle sintering resulting in larger particlesizes. Some controlled sintering of the particles can be performed inthe oven at somewhat higher temperatures to produce slightly larger,average particle diameters.

For the metal incorporation into vanadium oxide, the temperaturegenerally ranges from about 50° C. to about 500° C., preferably fromabout 80° C. to about 400° C., and more preferably from about 80° C. toabout 325° C. The processing temperature can range from about 80° C. toabout 250° C. The particles preferably are heated for about 5 minutes toabout 100 hours. Some empirical adjustment may be required to producethe conditions appropriate for yielding a desired material.

C. Particle Properties

A collection of particles of interest, comprising metal vanadium oxidecompounds, generally has an average diameter for the primary particlesof less than about 500 nm, preferably from about 5 nm to about 100 nm,more preferably from about 5 nm to about 50 nm, and even more preferablyfrom about 5 nm to about 25 nm. The primary particles usually have aroughly spherical gross appearance. Upon closer examination, crystallineparticles generally have facets corresponding to the underlying crystallattice. Nevertheless, crystalline primary particles tend to exhibitgrowth that is roughly equal in the three physical dimensions to give agross spherical appearance. In preferred embodiments, 95 percent of theprimary particles, and preferably 99 percent, have ratios of thedimension along the major axis to the dimension along the minor axisless than about 2. Diameter measurements on particles with asymmetriesare based on an average of length measurements along the principle axesof the particle.

Because of their small size, the primary particles tend to form looseagglomerates due to van der Waals and other electromagnetic forcesbetween nearby particles. Nevertheless, the nanometer scale of theprimary particles is clearly observable in transmission electronmicrographs of the particles. The particles generally have a surfacearea corresponding to particles on a nanometer scale as observed in themicrographs. Furthermore, the particles can manifest unique propertiesdue to their small size and large surface area per weight of material.For example, vanadium oxide nanoparticles generally exhibit surprisinglyhigh energy densities in lithium batteries, as described in copendingand commonly assigned U.S. patent application Ser. No. 08/897,776 nowU.S. Pat. No. 5,952,125, entitled “Batteries With ElectroactiveNanoparticles,” incorporated herein by reference.

The primary particles preferably have a high degree of uniformity insize. Laser pyrolysis, as described above, generally results inparticles having a very narrow range of particle diameters. Furthermore,heat processing under mild conditions does not alter the very narrowrange of particle diameters. With aerosol delivery, the distribution ofparticle diameters is particularly sensitive to the reaction conditions.Nevertheless, if the reaction conditions are properly controlled, a verynarrow distribution of particle diameters can be obtained with anaerosol delivery system, as described above. As determined fromexamination of transmission electron micrographs, the primary particlesgenerally have a distribution in sizes such that at least about 95percent, and preferably 99 percent, of the primary particles have adiameter greater than about 40 percent of the average diameter and lessthan about 160 percent of the average diameter. Preferably, the primaryparticles have a distribution of diameters such that at least about 95percent, and preferably 99 percent, of the primary particles have adiameter greater than about 60 percent of the average diameter and lessthan about 140 percent of the average diameter.

Furthermore, in preferred embodiments no primary particles have anaverage diameter greater than about 4 times the average diameter andpreferably 3 times the average diameter, and more preferably 2 times theaverage diameter. In other words, the particle size distributioneffectively does not have a tail indicative of a small number ofparticles with significantly larger sizes. This is a result of the smallreaction region and corresponding rapid quench of the particles. Aneffective cut off in the tail of the size distribution indicates thatthere are less than about 1 particle in 10⁶ have a diameter greater thana specified cut off value above the average diameter. Narrow sizedistributions, lack of a tail in the distributions and the roughlyspherical morphology can be exploited in a variety of applications.

In addition, the nanoparticles generally have a very high purity level.The crystalline metal vanadium oxide nanoparticles produced by the abovedescribed methods are expected to have a purity greater than thereactants because the crystal formation process tends to excludecontaminants from the lattice. Furthermore, crystalline vanadium oxideparticles produced by laser pyrolysis have a high degree ofcrystallinity. Similarly, the crystalline metal vanadium oxidenanoparticles produced by heat processing have a high degree ofcrystallinity. Impurities on the surface of the particles may be removedby heating the particles to achieve not only high crystalline purity buthigh purity overall.

Vanadium oxide has an intricate phase diagram due to the many possibleoxidation states of vanadium. Vanadium is known to exist in oxidationstates between V⁺² and V⁺⁵. The energy differences between the oxides ofvanadium in the different oxidation states is not large. Therefore, itis possible to produce stoichiometric mixed valence compounds. Knownforms of vanadium oxide include VO, VO_(1.27), V₂O₃, V₃O₅, VO₂, V₆O₁₃,V₄O₉, V₃O₇, and V₂O₅. Laser pyrolysis alone or with additional heatingcan successfully yield single phase vanadium oxide in many differentoxidation states, as evidenced by x-ray diffraction studies. Thesesingle phase materials are generally crystalline, although someamorphous nanoparticles have been produced. The heat treatmentapproaches are useful for increasing the oxidation state of vanadiumoxide particles or for converting vanadium oxide particles to moreordered phases.

There are also mixed phase regions of the vanadium oxide phase diagram.In the mixed phase regions, particles can be formed that have domainswith different oxidation states, or different particles can besimultaneously formed with vanadium in different oxidation states. Inother words, certain particles or portions of particles have onestoichiometry while other particles or portions of particles have adifferent stoichiometry. Mixed phase nanoparticles have been formed.Non-stoichiometric materials also can be formed.

The vanadium oxides generally form crystals with octahedral or distortedoctahedral coordination. Specifically, VO, V₂O₃, VO₂, V₆O₁₃ and V₃O₇ canform crystals with octahedral coordination. In addition, V₃O₇ can formcrystals with trigonal bipyramidal coordination. V₂O₅ forms crystalswith square pyramidal crystal structure. V₂O₅ recently also has beenproduced in a two dimensional crystal structure. See, M. Hibino, et al.,Solid State Ionics 79:239-244 (1995), incorporated herein by reference.When produced under appropriate conditions, the vanadium oxidenanoparticles can be amorphous. The crystalline lattice of the vanadiumoxide can be evaluated using x-ray diffraction measurements.

Metal vanadium oxide compounds can be formed with variousstoichiometries. U.S. Pat. No. 4,310,609 to Liang et al., entitled“Metal Oxide Composite Cathode Material for High Energy DensityBatteries,” incorporated herein by reference, describes the formation ofAg_(0.7)V₂O_(5.5), AgV₂O_(5.5), and Cu_(0.7)V₂O_(5.5). The production ofoxygen deficient silver vanadium oxide, Ag_(0.7)V₂O₅, is described inU.S. Pat. No. 5,389,472 to Takeuchi et al., entitled “Preparation ofSilver Vanadium Oxide Cathodes Using Ag(O) and V₂O₅ as StartingMaterials,” incorporated herein by reference. The phase diagram ofsilver vanadium oxides of the formula Ag_(x)V₂O_(y) are described inpublished European Patent Application 0 689 256A, entitled “Cathodematerial for nonaqueous electrochemical cells,” incorporated herein byreference.

D. Batteries

Referring to FIG. 8, battery 450 has an negative electrode 452, apositive electrode 454 and separator 456 between negative electrode 452and positive electrode 454. A single battery can include multiplepositive electrodes and/or multiple negative electrodes. Electrolyte canbe supplied in a variety of ways as described further below. Battery 450preferably includes current collectors 458, 460 associated with negativeelectrode 452 and positive electrode 454, respectively. Multiple currentcollectors can be associated with each electrode if desired.

Lithium has been used in reduction/oxidation reactions in batteriesbecause it is the lightest metal and because it is the mostelectropositive metal. Certain forms of metal oxides are known toincorporate lithium ions into its structure through intercalation orsimilar mechanisms such as topochemical absorption. Intercalation oflithium ions can take place also into suitable forms of a vanadium oxidelattice as well as the lattice of the metal vanadium oxide composition.

In particular, lithium intercalates into the vanadium oxide lattice ormetal vanadium oxide lattice during discharge of the battery. Thelithium leaves the lattice upon recharging, i.e., when a voltage isapplied to the cell such that electric current flows into the positiveelectrode due to the application of an external EMF to the battery.Positive electrode 454 acts as a cathode during discharge, and negativeelectrode 452 acts as an anode during discharge of the cell. Metalvanadium oxide particles can be used directly in a positive electrodefor a lithium based battery to provide a cell with a high energydensity. Appropriate metal vanadium oxide particles can be an effectiveelectroactive material for a positive electrode in either a lithium orlithium ion battery.

Positive electrode 454 includes electroactive nanoparticles such asmetal vanadium oxide nanoparticles held together with a binder such as apolymeric binder. Nanoparticles for use in positive electrode 454generally can have any shape, e.g., roughly spherical nanoparticles orelongated nanoparticles. In addition to metal vanadium oxide particles,positive electrode 454 can include other electroactive nanoparticlessuch as TiO₂ nanoparticles, vanadium oxide nanoparticles and manganeseoxide nanoparticles. The production of TiO₂ nanoparticles has beendescribed, see U.S. Pat. No. 4,705,762, incorporated herein byreference. Vanadium oxide nanoparticles are know to exhibit surprisinglyhigh energy densities, as described in copending and commonly assignedU.S. patent application Ser. No. 08/897,776 now U.S. Pat. No. 5,952,125,entitled “Batteries With Electroactive Nanoparticles,” incorporatedherein by reference. The production of manganese oxide nanoparticles isdescribed in copending and commonly assigned U.S. patent applicationSer. No. 09/188,770 to Kumar et al. filed on Nov. 9, 1998, now U.S. Pat.No. 6,506,493, entitled “Metal Oxide Particles,” incorporated herein byreference.

While some electroactive materials are reasonable electrical conductors,a positive electrode generally includes electrically conductiveparticles in addition to the electroactive nanoparticles. Thesesupplementary, electrically conductive particles generally are also heldby the binder. Suitable electrically conductive particles includeconductive carbon particles such as carbon black, metal particles suchas silver particles, metal fibers such as stainless steel fibers, andthe like.

High loadings of particles can be achieved in the binder. Particlespreferably make up greater than about 80 percent by weight of thepositive electrode, and more preferably greater than about 90 percent byweight. The binder can be any of various suitable polymers such aspolyvinylidene fluoride, polyethylene oxide, polyethylene,polypropylene, polytetrafluoro ethylene, polyacrylates,ethylene-(propylene-diene monomer) copolymer (EPDM) and mixtures andcopolymers thereof.

Negative electrode 452 can be constructed from a variety of materialsthat are suitable for use with lithium ion electrolytes. In the case oflithium batteries, the negative electrode can include lithium metal orlithium alloy metal either in the form of a foil, grid or metalparticles in a binder.

Lithium ion batteries use particles of an composition that canintercalate lithium. The particles are held with a binder in thenegative electrode. Suitable intercalation compounds include, forexample, graphite, synthetic graphite, coke, mesocarbons, doped carbons,fullerenes, niobium pentoxide, tin alloys, SnO₂ and mixtures andcomposites thereof.

Current collectors 458, 460 facilitate flow of electricity from battery450. Current collectors 458, 460 are electrically conductive andgenerally made of metal such as nickel, iron, stainless steel, aluminumand copper and can be metal foil or preferably a metal grid. Currentcollector 458, 460 can be on the surface of their associated electrodeor embedded within their associated electrode.

The separator element 456 is electrically insulating and provides forpassage of at least some types of ions. Ionic transmission through theseparator provides for electrical neutrality in the different sectionsof the cell. The separator generally prevents electroactive compounds inthe positive electrode from contacting electroactive compounds in thenegative electrode.

A variety of materials can be used for the separator. For example, theseparator can be formed from glass fibers that form a porous matrix.Preferred separators are formed from polymers such as those suitable foruse as binders. Polymer separators can be porous to provide for ionicconduction. Alternatively, polymer separators can be solid electrolytesformed from polymers such as polyethylene oxide. Solid electrolytesincorporate electrolyte into the polymer matrix to provide for ionicconduction without the need for liquid solvent.

Electrolytes for lithium batteries or lithium ion batteries can includeany of a variety of lithium salts. Preferred lithium salts have inertanions and are nontoxic. Suitable lithium salts include, for example,lithium hexafluorophosphate, lithium hexafluoroarsenate,lithiumbis(trifluoromethyl sulfonyl imide), lithium trifluoromethanesulfonate, lithium tris(trifluoromethyl sulfonyl) methide, lithiumtetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate,lithium chloride and lithium perfluorobutane.

If a liquid solvent is used to dissolve the electrolyte, the solventpreferably is inert and does not dissolve the electroactive materials.Generally appropriate solvents include, for example, propylenecarbonate, dimethyl carbonate, diethyl carbonate, 2-methyltetrahydrofuran, dioxolane, tetrahydrofuran, 1,2-dimethoxyethane,ethylene carbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile,formamide, dimethyl formamide and nitromethane.

The shape of the battery components can be adjusted to be suitable forthe desired final product, for example, a coin battery, a rectangularconstruction or a cylindrical battery. The battery generally includes acasing with appropriate portions in electrical contact with currentcollectors and/or electrodes of the battery. If a liquid electrolyte isused, the casing should prevent the leakage of the electrolyte. Thecasing can help to maintain the battery elements in close proximity toeach other to reduce resistance within the battery. A plurality ofbattery cells can be placed in a single case with the cells connectedeither in series or in parallel.

EXAMPLES Example 1 Production of Vanadium Oxide by Laser Pyrolysis

Single phase VO₂ particles were produced by laser pyrolysis. The VOCl₃(Strem Chemical, Inc., Newburyport, Mass.) precursor vapor was carriedinto the reaction chamber by bubbling Ar gas through the VOCl₃ liquidstored in a container at room temperature. The reactant gas mixturecontaining VOCl₃, Ar, O₂ and C₂H₄ was introduced into the reactant gasnozzle for injection into the reactant chamber. The reactant gas nozzlehad dimensions ⅝ in×⅛ in. C₂H₄ gas was used as a laser absorbing gas.Argon was used as an inert gas.

The synthesized vanadium oxide nanoscale particles can be directlyhandled in the air. Representative reaction conditions for theproduction of this material are described in Table 1.

TABLE 1 Phase VO₂ Crystal Monoclinic Structure Pressure 210 (Torr)Argon-Win 700 (sccm) Argon-Sld. 7.0 (slm) Ethylene (slm) 1.61 CarrierGas- 1.4 Argon (slm) Oxygen (slm) 0.47 Precursor 40 Temp. (° C.)Production 35 Rate (gm/hr) Laser Power- 780 Input (watts) Laser Power-640 Output (watts) sccm = standard cubic centimeters per minute slm =standard liters per minute Argon-Win. = argon flow through inlets 216,218 Argon-Sld. = argon flow through annular channel 142

An x-ray diffractogram of representative product nanoparticles is shownin FIG. 9. Clear diffraction peaks corresponding to a monocliniccrystalline structure are visible. The identified structure from thediffractogram is almost identical to that of the corresponding bulkmaterial, which has larger particle sizes.

Example 2 Heat Treatment to Form Crystalline V₂O₅ Nanoparticles

The starting materials for the heat treatment were VO₂ nanoparticlesproduced by laser pyrolysis according to the parameters in Table 1.

The nanoparticles were heat treated at in an oven roughly as shown inFIG. 6. The particles were fed in batches of between about 100 grams toabout 150 grams into the glass jar. Oxygen is fed through a ⅛″ stainlesssteel tube at an oxygen flow rate of 155 cc/min. A mixing speed of 5 rpmwas used to constantly mix the powders during the heat treatment. Thepowders were heated for 30 minutes at 100° C., then for 30 minutes at200° C. and finally at 230° C. for 16 hours. A heating rate of 4°C./minute was used to heat the samples to the target temperatures. Theresulting nanoparticles were single phase crystalline V₂O₅nanoparticles. The x-ray diffractogram of this material is shown in FIG.10. From the x-ray diffractogram, it could be determined that theresulting particles were orthorhombic V₂O₅.

TEM photographs were obtained of representative nanoparticles followingheat treatment. The TEM photograph is shown in FIG. 11. An approximatesize distribution was determined by manually measuring diameters of theparticles shown in FIG. 11. The particle size distribution is shown inFIG. 12. An average particle size of about 10-11 nm was obtained. Onlythose particles showing clear particle boundaries were measured andrecorded to avoid regions distorted in the micrograph. This should notbias the measurements obtained since the single view of the micrographmay not show a clear view of all particles because of the orientation ofthe crystals.

Example 3 Heat Processing to Form Silver Vanadium Oxide

This example demonstrates the production of nanoscale silver vanadiumoxide using a vanadium oxide nanoparticle starting material. The silvervanadium oxide is produced by a heat processing.

About 9.5 g of silver nitrate (AgNO₃) was dissolved into about 15 ml ofdeionized water. Then, about 10 g of V₂O₅ nanoparticles produced asdescribed in Examples 2 were added to the silver nitrate solution toform a mixture. The resulting mixture was stirred on a magnetic stirrerfor about 30 minutes. After the stirring was completed the solution washeated to about 160° C. in an oven to drive off the water. The driedpowder mixture was ground with a mortar and pestle.

Six samples from the resulting ground powder weighing between about 100and about 300 mg of nanoparticles were placed separately into an open 1cc boat. The boat was placed within the quartz tube projecting throughan oven to perform the heat processing. The oven was essentially asdescribed above with respect to FIG. 7. Oxygen gas or argon gas wasflowed through a 1.0 in diameter quartz tube at a flow rate of about 20sccm. The samples were heated in the oven under the followingconditions:

-   -   1) 250° C., 60 hrs in argon    -   2) 250° C., 60 hrs in oxygen    -   3) 325° C., 4 hrs in argon    -   4) 325° C., 4 hrs in oxygen    -   5) 400° C., 4 hrs in argon    -   6) 400° C., 4 hrs in oxygen.        The samples were heated at approximately the rate of 2° C./min.        and cooled at the rate of approximately 1° C./min. The times        given above did not include the heating and cooling time.

The structure of the particles following heating was examined by x-raydiffraction. The x-ray diffractograms for the samples heated in oxygenand in argon are shown in FIGS. 13 and 14, respectively. All of theheated samples produces diffractograms with peaks indicating thepresence of Ag₂V₄O₁₁. The samples heated at 400° C. appear to lacksignificant amounts of V₂O₅. Heating the samples for somewhat longertimes at the lower temperatures should eliminate any remaining portionsof the V₂O₅ starting material.

A transmission electron micrograph of the silver vanadium oxideparticles is shown in FIG. 15. For comparison, a transmission electronmicrograph of the V₂O₅ nanoparticle sample used to form the silvervanadium oxide nanoparticles is shown in FIG. 16, at the same scale asFIG. 15. The V₂O₅ nanoparticles in FIG. 16 were produced underconditions similar to the conditions described in Examples 1 and 2. Thesilver vanadium oxide particles in FIG. 15 surprisingly have a slightlysmaller average diameter than the vanadium oxide nanoparticle startingmaterial in FIG. 16.

The embodiments described above are intended to be illustrative and notlimiting. Additional embodiments are within the claims below. Althoughthe present invention has been described with reference to preferredembodiments, workers skilled in the art will recognize that changes maybe made in form and detail without departing from the spirit and scopeof the invention.

1. A collection of particles comprising metal vanadium oxide, theparticles having an average diameter less than about 1 micron andwherein less than about 1 particle in 10⁶ has a diameter greater thanabout four times the average diameter of the collection of particles. 2.The collection of particles of claim 1 wherein the particles have anaverage diameter from about 5 nm to about 100 nm.
 3. The collection ofparticles of claim 1 wherein the particles have an average diameter fromabout 5 nm to about 50 nm.
 4. The collection of particles of claim 1wherein less than about 1 particle in 10⁶ has a diameter greater thanabout two times the average diameter of the collection of particles. 5.The collection of particles of claim 1 wherein the particles have anaverage diameter less than about 500 nm.
 6. The collection of particlesof claim 1 wherein the metal vanadium oxide is crystalline.
 7. A batterycomprising a positive electrode having active particles comprising metalvanadium oxide within a binder, the active particles having an averagediameter less than about 1 micron and wherein the collection ofparticles has a distribution of particle sizes such that at least about95 percent of the particles have a diameter greater than about 40percent of the average diameter and less than about 160 percent of theaverage diameter.
 8. The collection of particles of claim 7 wherein thecollection of particles have a distribution of particle sizes such thatat least about 95 percent of the particles have a diameter greater thanabout 60 percent of the average diameter and less than about 140 percentof the average diameter.
 9. A battery comprising a positive electrodehaving active particles comprising metal vanadium oxide within a binder,the active particles having an average diameter less than about 1 micronand wherein less than about 1 particle in 10⁶ has a diameter greaterthan about four times the average diameter of the collection ofparticles.
 10. The battery of claim 9 wherein the active particles havean average diameter from about 5 nm to about 100 nm.
 11. The battery ofclaim 9 wherein the positive electrode further comprises supplementary,electrically conductive particles.
 12. The battery of claim 9 whereinless than about 1 active particle in 10⁶ have a diameter greater thanabout two times the average diameter of the collection of activeparticles.
 13. The battery of claim 9 wherein the active particles havean average diameter less than about 500 nm.
 14. The battery of claim 9wherein the metal vanadium oxide is crystalline.
 15. A collection ofparticles comprising metal vanadium oxide, the particles having anaverage diameter less than about 1 micron and wherein the collection ofparticles has a distribution of particle sizes such that at least about95 percent of the particles have a diameter greater than about 40percent of the average diameter and less than about 160 percent of theaverage diameter.
 16. The collection of particles of claim 15 whereinthe particles have an average diameter from about 5 nm to about 100 nm.17. The battery of claim 16 wherein the collection of particles have adistribution of particle sizes such that at least about 95 percent ofthe particles have a diameter greater than about 60 percent of theaverage diameter and less than about 140 percent of the averagediameter.
 18. The collection of particles of claim 15 wherein theparticles have an average diameter from about 5 nm to about 50 nm. 19.The battery of claim 7 wherein the particles have an average diameterfrom about 5 nm to about 100 nm.
 20. The battery of claim 7 wherein theparticles have an average diameter from about 5 nm to about 50 nm.